Fluoropolymers that are available in the form of anionically, cationically, or nonionically dispersed fluorinated polymer emulsions are commonly used as soil resist agents for fibrous substrates, such as carpets, rugs, and textiles. Such soil resist agents act by providing water- and oil-repellency and soil resistance to treated substrates. Resistance to acid dye stains such as food and beverage stains is provided by solutions of hydrolyzed maleic anhydride copolymers, copolymers of methacrylic acid and esters thereof, or sulfonated phenolic resins and blends thereof. An example of a food and beverage stain is the acid dye stain FD&C Red #40, commonly used in beverages.
Most commercially available fluorinated polymers useful as treating agents for imparting surface effects to substrates contain predominately eight or more carbons in the perfluoroalkyl chain to provide the desired repellency properties. Honda et al., in Macromolecules, 2005, 38, 5699-5705 show that for perfluoroalkyl chains of 8 carbons or greater, orientation of the perfluoroalkyl groups is maintained in a parallel configuration, while reorientation occurs for such chains having 6 carbon atoms or less. Such reorientation decreases surface properties such as receding contact angle. Thus, shorter chain perfluoroalkyls have traditionally not been successful commercially.
It is desired to improve surface effects, in particular soil resistance, of fibrous substrates, and to increase the fluorine efficiency; i.e., boost the efficiency or performance of treating agents so that lesser amounts of the expensive fluorinated polymer are required to achieve the same level of performance, or so that better performance is achieved using the same level of fluorine. It is desirable to reduce the chain length of the perfluoroalkyl groups thereby reducing the amount of fluorine present, while still achieving the same or superior surface effects.
Payet et al. in U.S. Pat. No. 4,875,901, disclosed the use of divalent metal salts, such as magnesium salts, as additives to stabilize fluorochemical oil and water repellents and stain resist resins in the treatment bath for coapplication of soil resist and stain resist agents. However, as noted by Pacifici in U.S. Pat. No. 6,616,856, Payet's single step process did not gain commercial acceptance, primarily due to inconsistent water and oil repellency effectiveness and its consequent failure to meet carpet industry standards. The inconsistency resulted from the stain-resist's tendency to interfere with the fluorochemical soil resist curing process, a thermal reorientation of the fluorochemical molecules. Pacifici substituted a naphthalene-sulfonated salt as a fluorochemical anti-coalescing agent in a single bath process. Pacifici did not address the use of cationically dispersed fluorochemical-based repellent emulsions (as a soil resist agent) in combination with stain resists.
There is a need for copolymer compositions that impart significant soil resistance to fibrous substrates while having perfluoroalkyl groups with six or less carbon atoms. There is also a need for additives that allow for such soil resist agents to be combined with other treatment agents, such as stain resist agents, in aqueous dilutions to be applied simultaneously while still enhancing the soil resist performance. The present invention provides such compositions.